AP Biology AP Biology John D. O’Bryant School of Mathematics and Science October 11, 2012

AP Biology Agenda  Do Now (Quiz)  Experimental Design: Lactose Intolerance, etc.

AP Biology Do Now (Quiz)  1. Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity in the cell?  A) cessation of all enzyme formation B) compartmentalization of enzymes into defined organelles C) exporting enzymes out of the cell D) connecting enzymes into large aggregates E) hydrophobic interactions

AP Biology Do Now (Quiz)  2. Which of the following is an example of cooperativity?  A) the binding of an end product of a metabolic pathway to the first enzyme that acts in the pathway B) protein function at one site affected by binding at another of its active sites C) a molecule binding at one unit of a tetramer allowing faster binding at each of the other three D) the effect of increasing temperature on the rate of an enzymatic reaction E) binding of an ATP molecule along with one of the substrate molecules in an active site

AP Biology Do Now (Quiz)  3. Which of the following is the most correct interpretation of the figure? A) Inorganic phosphate is created from organic phosphate. B) Energy from catabolism can be used directly for performing cellular work. C) ADP + Pi are a set of molecules that store energy for catabolism. D) ATP is a molecule that acts as an intermediary to store energy for cellular work. E) Pi acts as a shuttle molecule to move energy from ATP to ADP.

AP Biology Do Now (Quiz)  4. How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?  A) by binding at the active site of the enzyme B) by changing the shape of a reactant C) by changing the free energy change of the reaction D) by acting as a coenzyme for the reaction E) by decreasing the activation energy of the reaction

AP Biology Do Now (Quiz)  5. Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?  A) denaturization of the enzyme B) allosteric inhibition C) competitive inhibition D) saturation of the enzyme activity E) insufficient cofactors

AP Biology Metabolism & Enzymes

AP Biology Factors that Affect Enzymes

AP Biology Factors Affecting Enzyme Function  Enzyme concentration  Substrate concentration  Temperature  pH  Salinity  Activators  Inhibitors catalase

AP Biology Enzyme concentration enzyme concentration reaction rate What’s happening here?!

AP Biology Factors affecting enzyme function  Enzyme concentration  as  enzyme =  reaction rate  more enzymes = more frequently collide with substrate  reaction rate levels off  substrate becomes limiting factor  not all enzyme molecules can find substrate enzyme concentration reaction rate

AP Biology Substrate concentration substrate concentration reaction rate What’s happening here?!

AP Biology Factors affecting enzyme function substrate concentration reaction rate  Substrate concentration  as  substrate =  reaction rate  more substrate = more frequently collide with enzyme  reaction rate levels off  all enzymes have active site engaged  enzyme is saturated  maximum rate of reaction

AP Biology 37° Temperature temperature reaction rate What’s happening here?!

AP Biology Factors affecting enzyme function  Temperature  Optimum T°  greatest number of molecular collisions  human enzymes = 35°- 40°C  body temp = 37°C  Heat: increase beyond optimum T°  increased energy level of molecules disrupts bonds in enzyme & between enzyme & substrate  H, ionic = weak bonds  denaturation = lose 3D shape (3° structure)  Cold: decrease T°  molecules move slower  decrease collisions between enzyme & substrate

AP Biology Enzymes and temperature  Different enzymes function in different organisms in different environments 37°C temperature reaction rate 70°C human enzyme hot spring bacteria enzyme (158°F)

AP Biology How do ectotherms do it?

AP Biology 7 pH reaction rate pepsintrypsin What’s happening here?! pepsin trypsin

AP Biology Factors affecting enzyme function  pH  changes in pH  adds or remove H +  disrupts bonds, disrupts 3D shape  disrupts attractions between charged amino acids  affect 2° & 3° structure  denatures protein (end 10/11)  optimal pH?  most human enzymes = pH 6-8  depends on localized conditions  pepsin (stomach) = pH 2-3  trypsin (small intestines) = pH

AP Biology Salinity salt concentration reaction rate What’s happening here?!

AP Biology Factors affecting enzyme function  Salt concentration  changes in salinity  adds or removes cations (+) & anions (–)  disrupts bonds, disrupts 3D shape  disrupts attractions between charged amino acids  affect 2° & 3° structure  denatures protein  enzymes intolerant of extreme salinity  Dead Sea is called dead for a reason!

AP Biology Compounds which help enzymes  Activators  cofactors  non-protein, small inorganic compounds & ions  Mg, K, Ca, Zn, Fe, Cu  bound within enzyme molecule  coenzymes  non-protein, organic molecules  bind temporarily or permanently to enzyme near active site  many vitamins  NAD (niacin; B3)  FAD (riboflavin; B2)  Coenzyme A Mg in chlorophyll Fe in hemoglobin

AP Biology Compounds which regulate enzymes  Inhibitors  molecules that reduce enzyme activity  competitive inhibition  noncompetitive inhibition  irreversible inhibition  feedback inhibition

AP Biology Competitive Inhibitor  Inhibitor & substrate “compete” for active site  penicillin blocks enzyme bacteria use to build cell walls  disulfiram (Antabuse) treats chronic alcoholism  blocks enzyme that breaks down alcohol  severe hangover & vomiting 5-10 minutes after drinking  Overcome by increasing substrate concentration  saturate solution with substrate so it out-competes inhibitor for active site on enzyme

AP Biology Non-Competitive Inhibitor  Inhibitor binds to site other than active site  allosteric inhibitor binds to allosteric site  causes enzyme to change shape  conformational change  active site is no longer functional binding site  keeps enzyme inactive  some anti-cancer drugs inhibit enzymes involved in DNA synthesis  stop DNA production  stop division of more cancer cells  cyanide poisoning irreversible inhibitor of Cytochrome C, an enzyme in cellular respiration  stops production of ATP

AP Biology Irreversible inhibition  Inhibitor permanently binds to enzyme  competitor  permanently binds to active site  allosteric  permanently binds to allosteric site  permanently changes shape of enzyme  nerve gas, sarin, many insecticides (malathion, parathion…)  cholinesterase inhibitors doesn’t breakdown the neurotransmitter, acetylcholine

AP Biology Allosteric regulation  Conformational changes by regulatory molecules  inhibitors  keeps enzyme in inactive form  activators  keeps enzyme in active form Conformational changesAllosteric regulation

AP Biology Metabolic pathways A  B  C  D  E  F  GA  B  C  D  E  F  G enzyme 1  enzyme 2  enzyme 3  enzyme 4  enzyme 5  enzyme 6   Chemical reactions of life are organized in pathways  divide chemical reaction into many small steps  artifact of evolution   efficiency  intermediate branching points   control = regulation A  B  C  D  E  F  GA  B  C  D  E  F  G enzyme 

AP Biology Efficiency  Organized groups of enzymes  enzymes are embedded in membrane and arranged sequentially  Link endergonic & exergonic reactions Whoa! All that going on in those little mitochondria!

AP Biology allosteric inhibitor of enzyme 1 Feedback Inhibition  Regulation & coordination of production  product is used by next step in pathway  final product is inhibitor of earlier step  allosteric inhibitor of earlier enzyme  feedback inhibition  no unnecessary accumulation of product A  B  C  D  E  F  GA  B  C  D  E  F  G enzyme 1  enzyme 2  enzyme 3  enzyme 4  enzyme 5  enzyme 6  X

AP Biology Feedback inhibition  Example  synthesis of amino acid, isoleucine from amino acid, threonine  isoleucine becomes the allosteric inhibitor of the first step in the pathway  as product accumulates it collides with enzyme more often than substrate does threonine isoleucin e

AP Biology Don’t be inhibited! Ask Questions!

AP Biology Cooperativity  Substrate acts as an activator  substrate causes conformational change in enzyme  induced fit  favors binding of substrate at 2 nd site  makes enzyme more active & effective  hemoglobin Hemoglobin  4 polypeptide chains  can bind 4 O 2 ;  1 st O 2 binds  now easier for other 3 O 2 to bind

AP Biology Lorenzo’s Oil